U.S. Pat. No. 7,344,000 B2 discloses a materials handling vehicle comprising a base, such as a power unit, and a carriage assembly, such as a platform assembly, wherein the carriage assembly is movable relative to the base. The vehicle further comprises a cylinder coupled to the base to effect movement of the carriage assembly relative to the base and a hydraulic system to supply a pressurized fluid to the cylinder. The hydraulic system includes an electronically controlled valve coupled to the cylinder. The vehicle further comprises control structure to control the operation of the valve such that the valve is closed in the event of an unintended descent of the carriage assembly in excess of a commanded speed.